1. Field of the Invention
This invention relates generally to means for monitoring eye movement. In particular, this invention relates to an electronics circuit for calculating the position of a human eye at any given instant of time.
2. Description of the Prior Art
Heretofore numerous methods and apparatus have been employed for monitoring the position and movement of the human eye. Such apparatus are too numerous to discuss herewith. Besides, most thereof constitute prior art devices which are well known to the artisan, thereby obviating the need for further discussion thereof.
Of course, there are several prior art devices which are of some significance, inasmuch as they at least remotely or indirectly concern subject matter that is pertinent to the system constituting the instant circuit for calculating the position of the eye.
For example, U.S. Pat. No. 3,217,706 to G. H. Sullivan discloses an impedance oculograph which includes first and second pairs of electrodes adapted to be applied to the body surface near the eye, oscillator means for supplying a fixed amplitude carrier voltage to the first and second pairs of electrodes, first demodulator means connected to the first pair of electrodes for providing an electrical output signal corresponding to the vertical position of the eye with respect to a neutral position, and second demodulator means connected to the second pair of electrodes for providing an electrical output signal corresponding to the horizontal position of the eye with respect to the neutral position.
U.S. Pat. No. 3,473,868 to L. R. Young and J. S. Newman discloses a first pair of infrared light sensitive photo cells, which sense vertical eye movement, and a second pair of infrared light sensitive photocells, which sense horizontal eye movement. The output signals of the first pair of photocells are summed at a first transformer, amplified by a first operational amplifier, and fed to a first phase sensitive detector which produces an output signal only when an infrared light source is on. The output of the aforementioned detector is then directed through a filter which yields a DC signal proportional to vertical eye movement. In a like manner, the difference in the output signals of the second pair of photocells is determined by a second transformer, amplified by a second operational amplifier, and fed to a second phase sensitive detector which produces an output signal only when the above mentioned infrared light source is on. The output of the above mentioned detector is directed through a second filter so as to yield a DC signal which is a function of the horizontal eye position.
Unfortunately, the aforementioned devices of the prior art ordinarily leave something to be desired, especially from the standpoints of position measurement accuracy and response time, that is, the aforementioned devices of the prior art do not allow for position measurements at high rates. In addition, the aforementioned devices of the prior art do not operate in exactly the same manner as the subject invention and contain a combination of elements that is somewhat different from that of the present invention.